Wood Quality
- Three factors are considered for wood quality: color, texture, and figure.
Color of sapwood does not vary greatly among tree species, but color of
heartwood does. Chemicals called extractives give heartwood a great variety of
colors. Extractives are chemicals that act as natural preservatives.
Cellulose has a specific gravity of 1.53. Density of wood depends on how
closely the cellulose is packed and the amount of extractives in the wood.
Some tropical woods have specific gravity over 1, which means they do not
float. Texture is greatly dependent on size of cells and figure on cell
arrangements. But, the 3 characteristics -color, texture, figure-all
assume that the wood has not been altered by extrinsic agents. This is
highly unlikely in nature. Branches are always dying, protection zones
are failing, wounds are being inflicted, roots are dying, and all of these
events incite defense processes that cause chemical shunts to produce
protection chemicals, and changes in cell types and arrangements. It
is difficult to think of a tree that has not had many injuries. As a
result, cells are different, and cell arrangements are altered. A tree
with high quality wood has few extrinsic disturbances, or the tree has an
effective compartmentalization process that keeps all infections walled off
to smaller volumes of wood. A major point is that trees will have
wounds and dying branches and, in a sense, these problems become part of the
"normal" processes. To talk about wood quality without considering
these points is foolish.